Beater bar mill with two beater bar disks rotating rapidly in opposite directions



Feb. 20, 1934. J. o

HEATER BAR MILL WITH TWO BEATER BAR DISKS ROTATING RAPIDLY IN OPPOSITEDIRECTIONS 2 Sheets-Sheet 1 Filed June 12, 1931 U I e Feb. 20, 1934.

J. o'r'r 1,947,953 HEATER BAR MILL WITH TWO BEATER BAR DISKS ROTATINGRAPIDLY IN OPPOSITE DIRECTIONS Filed June 12. 1931 2 Sheets-Sheet 2 gymnewton Patented Feb. '20, 1934 UNITED STATES PATENT OFFICE BEATER BARMILL WITH Two BEATER BAR DISKS ROTATING RAPIDLY IN OP- POSITE DIRECTIONSJosef Otto, Cologne-Lindenthal, Germany 7 Claims.

Applications for patent filed in Germany June 13, 1930, and August 5,1930.

In beater bar mills for grinding material finely which are provided withtwo grinding disks rapidly rotating with respect to each other on ahorizontal shaft the main difficulty resides in effecting theintroduction of the material to be ground in such manner that it isdistributed uniformly over the entire periphery of the rotating beaterbars or mill teeth. It is only when the material is uniformlydistributed that a high performance and a constantly good grinding isensured because otherwise only a part of the beater bars is operativeand at the overloaded points larger particles can readily slip throughwithout being pulverized by beating. Also if the material to be groundis not uniformly distributed the wear of the machine is increased andits operation is unsteady. In the case of moist and sticky material itis only possible to grind it when it is uniformly distributed over theentire grinding chamber as otherwise the machine im-- mediately jams atthe overloaded points.

It has already been proposed to provide the rotating grinding disks withcentrifugal vanes. In this way however it is not possible to obtain ageneral distribution of the material as it can fall from the charginghopper directly into the lower part of the grinding zone between thevanes which are directed downwardly. No improvement can be obtained byproviding a distributing cone for the material which cone is disposedbetween the centrifugal vanes with a view to affording uniformdistribution, as in this case also the material is free to pass beyondthe cone into the lower portion of the grinding zone.

All the disadvantages above set forth are overcome in the presentinvention in that the centrifugal vanes or scoops disposed close to therow of bars are mounted helically on a deflecting cone of a hubassisting the introduction of the material, the cone being disposed onthe shaft of the mill and tapering conically towards the point at whichthe material is introduced and the vanes dividing in an approximatelyradial direction the inlet passage of approximately constant annularcross section formed at the hub. In this arrangement the materialsupplied vertically from above from the supply hopper is directedaxially by the centrifugal scoops which in consequence of their conicalarrangement deflect it in the radial direction and scatter it and at thesame time effect a distribution over the entire length of the beaterbars. In this way a stop is provided at the same time by thedistributing arrangement between the supply hopper and the grinding zoneso that the material supplied cannot fall directly into the grindingchamber in a non-uniform manner.

One embodiment of the invention is shown by way of example in thedrawings in which:

Fig. l is a vertical section through the beater bar mill (partly brokenaway),

Fig. 2 shows a perspective view of the hub serving for guiding thematerial introduced,

Fig. 3 shows also in perspective a ring of guide scoops, a part of theguide scoops being omitted.

Fig. 4 shows a vertical section through a somewhat modified beaterbar-mill (partly broken away).

The beater bar mill consists of the two grinding disks b and s which areequipped with concentric rings of beater bars and are secured on the twoshafts n and 0 which are rotated in opposite directions. Theintroduction of the material from the supply hopper 1 into the grindingzone is effected by the hub a of the grinding disc b. The hub isprovided with centrifugal scoops c which are arranged in such mannerthat the material supplied axially from the annular trough e cannot falldirectly between the scoops into the lower part of the grinding chamberbut that the material is drawn up by the scoops c and deflected in suchmanner that it is scattered on all sides in the radial direction and atthe same time is distributed over the entire length of the beater bars.The angle of the scoops is chosen in accordance with the peripheralspeed of the scoop wheel so that the material to be ground passes withthe initial speed determined by the height which it has fallen andwithout impacts between the scoops in the axial direction.

When adhesive and plastic material is being ground, the axial speed withwhich the material enters the space between the blades 0 of thecentrifugal wheel may become very much reduced. In order to insure,under such circumstances, a smooth and uniform flow of the material, theblades 0 must be inclined toward the wall of the casing in which thesupply channel (2 is arranged at a very small angle. But when soconstructed, the blades will be of excessive length and involve greatfrictional losses for the material to be ground. Such long blades,moreover, would result in large oblique cross-sections for the blades atthe side where the material enters, whereby the space through which thematerial enters would be considerably reduced in size and wherebynaturally also the capacity of the mill would be correspondinglyreduced. To overcome the aforementioned disadvantages, a guide bladering as shown in Fig. 3 may be disposed in that portion of the supplychannel e which faces the blade wheel, the blades of the guide bladering being inclined in a direction opposite to that of the blades 0 ofthe centrifugal wheel. When so arranged, the material to be groundenters through supply hopper f and passes under pressure into channel ewhere by means of the guide blades 9 it is-uniformly distributed overthe whole of the centrifugal wheel and smoothly fed between the blades0.

A special arrangement to protect the guide blade ring againstdisplacement is not needed, since the lateral edge p of channel e whichis turned toward the shaft n is provided with radial recesses in whichengage the guide blades 9.

The aforementioned disadvantages which present themselves when adhesivematerial is being ground can also be overcome by modifying thearrangement as shown in Fig. 4. According to Fig. 4, the blades care-provided with extended portions 2' which project into the supplychannel e at the side at which the material enters the mill. In all itsother details, the form of construction shown in 4 corresponds to thatshown in Fig. 1.

The inlet hub a, the centrifugal scoops c of which serve at the sametime as spokes for the grinding disk I), is preferably adapted to beinterchangeable so that a centrifugal wheel with centrifugal scoops c ofsuitable obliquity can be used to suit the material to be pulverized.

What I claim is:

i. In a mill of the kind described, a pair of coaxial and independentlyrotatable shafts adapted to rotate in opposite directions, a hub on oneof said shafts provided with an annular peripheral channel. and with anopening leading from channel through an end of the hub, helical feedermeans extending from the openin the end face of the hub to the other endof the hub, a disk carried by said hub, a second disk carried by theremaining shaft and spaced from the first disk, and beater bars carriedby the proximal faces of said disks with the bars of one disk interposedbetyeen the bars of the other disk.

2. In a mill of the kind described, a pair of coaxial and independentlyrotatable shafts adapted to rotate in opposite directions, afrustoconoidal hub having a concave surface and mounted on one of saidshafts, helical feeder blades extending from said hub, a flange on oneend of the hub supported by said blades in spaced relation to the bodyof the hub to provide material inlet openings, a disk carried by saidhub, a second disk carried by the remaining shaft and spaced from thefirst disk, and beater bars carried by the proximal faces of said diskswith the bars of one disk interposed between the bars of the other disk.

3. In a mill of the kind described, a pair of coaxial and independentlyrotatable shafts adapted to rotate in opposite directions, a hub on oneof said shafts provided with helical feeder means extending from one endface of the hub to its periphery, a disk carried by said hub, a seconddisk carried by the remaining shaft and spaced from the first disk,beater bars carried by the proximal faces of said disks with the bars ofone disk interposed between the bars of the other disk, a casing havingan annular feeder channel wherewith said feeder means constantly com- Imunicate, and fixed guide members disposed between said hub and channelto direct material to said feeder means.

4. In a mill of the kind described, a pair of coaxial and independentlyrotatable shafts adapted to rotate in opposite directions, afrustoconoidal hub having a concave surface and mounted on one of saidshafts, helical feeder blades extending from said hub, a disk carried bysaid hub, a second disk carried by the remaining shaft and spaced fromthe first disk, beater bars carried by the proximal faces of said diskswith the bars of one disk interposed between the bars of the other disk,a casing having an annular feeder channel having an open side adjacentthe smaller end of the hub, and fixed guide members disposed betweensaid hub and channel and arranged to direct material to said blades.

5. In a mill of the kind described, a pair of coaxial and independentlyrotatable shafts adapted to rotate in opposite directions, a hub on oneof said shafts provided with helical feeder means extending from one endface of the hub to its periphery, a disk carried by said hub, a seconddisk carried by the remaining shaft and spaced from the first disk,beater bars carried by the proximal faces of said disks with the bars ofone disk interposed between the bars of the other disk, a casing havingan annular feeder channel open toward said hub, and feeder extensions onsaid feeder means extending into said channel to force material fromsaid channel and deliver it to the main portions of said feeder means.

6. In a mill of the kind described, a pair of coaxial and independentlyrotatable shafts adapted to rotate in opposite directions,afrustoconoidal hub having a concave surface and mounted on one of saidshafts, helical feeder blades extending from said hub, a disk carried bysaid hub, a second disk carried by the remaining shaft and spaced fromthe first disk, beater bars carried by the proximal faces of said diskswith the bars of one disk interposed between the bars of the other disk,a casing having an annular feeder channel open towards the hub at thesmaller end thereof, and extensions on said blades entering said channelto force material from said channel and deliver it to the main portionsof said blades.

7. In a mill of the kind described, a pair of coaxial and independentlyrotatable shafts adapted to rotate in opposite directions, a hubarranged on one of these shafts and provided with an annular channelbeginning at one of the front faces of the hub and extending in arelikeformation to the periphery of the hub, said annular channel beingsubdivided by helical blades, a disk carried by said hub, a second shaftsupporting a second similar opposed disk, each of the disks beingprovided with a plurality of concentric, lattice-like collars ofstationary beater bars, the beater bar collars of the two oppositelyarranged disks rotating in opposite directions coacting with each otherin such fashion that they are not in immediate contact with each other,said beater bars extending across the entire width of the space betweenthe disks forming the grinding area.

JOSEF OTTO.

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